Besides the useful buffering for signal consistency, this pedal’s main aim is to provide something for the guitarist who uses multiple guitars on a gig and needs to match the levels.
The idea is that the default 12 o’clock position on a Level knob with up to +/-12dB of adjustment is for your main guitar and you can, say, roll it back a touch moving from the single coils of a Strat to a Les Paul with humbuckers and a higher output.
There’s also a high-frequency knob that works on the sparkly top-end sheen, so you can subtly compensate for dark or overly spiky pickups. The pedal is always on, but the footswitch can be used to mute the signal, perhaps when tuning - a dedicated output keeps your tuner out of the audio signal path.
There’s also a switch that applies input capacitance to load guitar pickups - it’s a subtle effect but it’s a worthwhile tonal variant that may suit your setup.